Simulating firing stresses in gun barrels

ABSTRACT

Method of and apparatus for testing gun barrels by simulating firing stresses using a small explosive charge and an insert within the barrel, which defines an annular space in which the charge gases principally act. The charge is constrained on firing by a rupture plate or choke passage, to produce temperature and pressure characteristics similar to those of a real firing using a projectile.

IJnited States Patent Von Boutteville et al. Feb. 4, 1975 SIMULA'IING FIRING STRESSES IN GUN 2,448,203 8/1948 Africano 73/35 BARRELS 3,043,137 7/1962 Clark et al 73/167 3,568,600 3/1971 Nosler 73/167 X Inventorsl s g i i l fv 3,721,456 3/1973 McDonald 102/39 R x usse or orst e (itt e, Oberwinter, both of Germany FOREIGN PATENTS OR APPLICATIONS 1,213,644 3/1966 Germany 73/167 [73] Ass1gnee: Flrma Rhc1nmetaIlG.m.b.I-I.,

Dusseldorf Germany Primary Examiner-Richard C. Queisser [22] Fil d; J ly 19, 1972 Assistant ExaminerDanie1 M. Yasich Attorney, Agent, or Firm-Ernest G. Montague; Karl [21] Appl. No.: 273,270 F. Ross; Herbert Dubno [30] Foreign Application Priority Data ABSTRACT Aug. 7, 1971 Germany 2139735 M ho of and apparatus for testing gun barrels by simulating firing stresses using a small explosive [52] U.S. Cl 73/167, 73/35, 102/39 R Charge and an insert within the barrel, which defines [51] Int. Cl. G011 5/14, GOln 25/54 an annular space in which the charge gases principally [58] Field of Search 73/167, 35; 102/39 R act. The charge is constrained on firing by a rupture plate or choke passage, to produce temperature and [56] References Cited pressure characteristics similar to those of a real firing UNITED STATES PATENTS 113mg a P 1 2,377,425 6/1945 Jackson 73/35 X 3 Claims, 3 Drawing Figures PATEHTEU E 4W5 SHEET 2 OF 3 NQI PATEHTED E 41% 3, 863 .499

' SHEET 3 OF 3 SIMULATING FIRING STRESSES IN GUN BARRELS BACKGROUND OF THE INVENTION The present invention relates to a method of and an apparatus by which gun barrels may be subject to substantially the same stresses as when actually fired, without the expenditure involved in test firing using live ammunition and is primarily concerned with endurance tests normally requiring a large number of test firings.

Methods are known by which the stress imposed on a gun barrel is simulated by subjecting the interior of the barrel to hydraulic pressure. This method has the disadvantage that neither temperature effects due to the hot gases of a charge nor the temporary rise in the gas pressure curve is realistically simulated. The expenditure for hydraulic apparatus for the production of a pressure of 2,000-5,000 atmosphers (gauge) is considerable. It is therefore generally not practicable, in view of the cost involved, to test a complete gun barrel in this manner, the testing being confined to one section only, which is detached from the remainder of the barrel for the purpose.

Methods are also known in which an insert of smaller diameter than the barrel and having a loading chamber for practice cartridges, is placed in the barrel of a weapon. Practice cartridge apparatus of this kind is widely used not only for the purpose of producing a detonation sound similar to that accompanying actual firing, but also for the purpose of generating sufficient gas pressure to operate breech block parts, such as is required, as example, when gas-pressure loaders are used. Such apparatus is not capable of simulating the actual stress to which the barrel is subjected during firmg.

It is an object of the present invention to provide a method of and an apparatus for subjecting a barrel and breech block to the true firing stress.

SUMMARY OF THE INVENTION According to the present invention, the method of testing a barrel comprises the insertion into the interior of the barrel of an insert body occupying only part of the barrel diameter and leaving an annular cavity between the internal wall of the barrel and the external wall of the insert, the internal wall of the barrel being directly subjected to gas pressure by detonating a propulsive charge which is less than that normally used with an actual projectile firing.

The insert body reduces considerably the volume of the loading chamber, so that the gases of the charge are caused to act directly on the internal wall of the barrel. The expenditure involved is also greatly reduced owing to the absence of a projectile. In order to ensure that the pressure rise of the gases will be simulated realistically despite the absence of a projectile, the necessary initial restraint of the charge gases must be produced by other means. This can be achieved by a nozzle and- /or rupture plate in the outflow orifice of the gases from the charge.

With the reduced chamber volume a far smaller charge than that required for the actual firing is sufficient to produce a gas pressure and a temperature characteristic on the wall of the barrel which are in accordance with real conditions.

In accordance with a further feature of the present invention suitable bores and cavities in the insert body ensure that not only the barrel but also the breech block is subjected to the gas pressure in the same manner as in actual firing, so that the durability of the breech block may be tested at the same time as the barrel.

The charge can be accommodated either in the insert or in a-casing separate therefrom.

Various constructional versions are possible, according to whether importance is attached to the testing of a complete gun barrel without any major alterations thereto or whether it is preferred to carry out the tests on a short section thereof, which generally comprises only the loading chamber or breech end.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects will become more readily apparent from the following description with reference to by example only, will be clearly understood in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a gun barrel showing the insert body in position;

FIG. 2 is a longitudinal section through the breech part ofa gun barrel with insert body and charge casing;

FIG. 3 is a cross section taken along the lines A-B of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings and in particular to the apparatus shown in FIG. 1, this embodiment can be built into the original gun without any appreciable alterations to the barrel or breech block. The comparatively small recoil forces occurring with the simulated firing are absorbed by the gun carriage without difficulty.

As shown in the drawing the breech-end or rearward part of a gun barrel 1 has a loading chamber which can be closed by a sliding wedge-type breech block 3 displaceably mounted in a base 2. The insert body 4 of the simulator is fitted into the loading chamber and is sealed off at its ends from the internal wall of the barrel. For this purpose the rear end of the insert body is provided at A with a collar-shaped flange 5, which is inserted in a recess in the barrel by means of a sealing packing 6, while the front end is provided at B with peripheral packing seals 8. Between the ends A and B the insert body is of reduced diameter, to form an annular chamber 9 between its periphery and the internal wall of the barrel. In its rear range, the insert body is provided with a loading chamber for a cartridge 10 containing a propulsive charge. The loading chamber is changed via a nozzle 11, forming a thrust face for a rupture plate 12, into a lengthwise bore 13 extending forwardly and which is open to its front.

According to the known principles of nozzle-type guns, the rupture plate and nozzle can be dimensioned in accordance with the loading and combustion chamber parameters, such that the gas pressure takes the desired course over a period of time. The insert body is also provided, in the region behind the rupture plate, (i.e. between the latter and the cartridge) with radial bores 14, which communicate the loading chamber with the annular chamber 9.

When the breech block is closed, the wedge-type breech block 3 rests against an annular seal 15, which is situated within an annular flange 5 of the insert and also against the base 16 of the propulsive charge casing. The diameter D, of the annular seal and the latter itself correspond to the bore of the barrel to be tested. Between the seal 15 and the seating of the base 16 of the charge casing, the flange has a recess by which a discshaped chamber 17, is created. This chamber is connected via longitudinal bores 18, and via an annular groove 19, provided in the insert, with the annular chamber 9.

When the propulsive charge is detonated, by a striker or electrically, the gases of the charge pass through the bores 14 into the annular chamber 9, where they act on the internal wall of the gun barrel, between the ends A and B of the insert, with the same gas pressure and approximately the same gas temperatures as in actual firing. Furthermore, the gases flow through the annular groove 19 and the bores 18 into the chamber 17, in which, in conjunction with the gas pressure acting on the base 16 of the charge casing, they exert a pressure on the breech block wedge and the annular seal 15, which corresponds to an actual firing.

In order to ensure that parts of the charge which have not burnt do not pass through the bores 14 into the annular chamber 9, it is advisable for the charge, to be detonated from the front, by means of a built-in detonator.

The charge is selected, as regards properties and quantity, so that the course taken by the gas pressure will correspond to that prevailing in a real firing of a projectile in the gun.

In the selection of the dimensions for the bores and gaps, it must be borne in mind that although the charge required for the simulator is reduced by keeping the entire combustion chamber small, yet excessively narrow bores will result in a high pressure drop to the internal wall of the barrel and to the breech block wedge.

In FIG. 2, a further embodiment of the apparatus is disclosed. In this case only the rear part 1 of a barrel, which is subjected to the maximum stress and which comprises the loading chamber and the starting range of the barrel, in place of the entire barrel of the gun.

An existing whole barrel can be effectively shortened to the necessary length as required.

The shortened barrel 1' can be closed at the rear with the normal breech 2 and the wedge 3.

In addition to the insert body 4, which serves mainly to reduce the volume of the loading chamber, a casing 20 accommodating the propulsive charge or the cartridge, respectively, can be inserted in the loading chamber.

The gap between the casing 20 and the barrel 1 can be sealed at the rear, for example, by means ofa plastic annular seal 29.

The insert body 4' is guided in the barrel 1 by ribs 21, while at the front it is screwed into a pressure plate 22. The axial gas force acting on the insert body 4', is transmitted from the pressure plate 22 via a sealing piece 23 and the screw-fitted casing tube 24 to the base 2. The casing tube 24 is separated by an air gap from the barrel 1 and is provided with apertures 25 which enable probes for measuring pressure, expansion and temperature to be affixed to the barrel 1.

In the sealing piece 23 is provided a rupture plate 12 which is introduced from the front, prior to the simulated firing, and pressed against an annular seating surface by a hollow clamp screw 27.

After the detonation of the propulsive charge, the gases of the charge sweep along the entire wall of the loading chamber and pass through apertures 26 in the pressure plate 22 (FIG. 3) into the chamber 28 in front of the rupture plate 12'. Up to the rupture of this plate 12, a gas pressure builds up in the entire loading chamber, as in the embodiment shown in FIG. 1. By appropriate selection of a suitable charge and of the correct dimensions for the combustion chamber and the appropriate construction of the rupture plate 12' gas pressure characteristics can be obtained, which correspond to those of an actual firing.

A feature of the embodiment disclosed in FIG. 2 resides in the fact that the wall of the barrel can be subjected to gases as far as the start of the drawn part of the barrel proper.

Although the embodiment disclosed in FIG. 2, it is necessary to make certain modifications to the barrel, it will generally be possible for the latter to be mounted in a normal gun carriage for the purpose of tests.

We claim: 1. An apparatus for testing gun barrels by simulating actual firing stresses without a projectile therein comprising:

a gun barrel; an insert body mounted in the loading chamber of said gun barrel to reduce the volume of said loading chamber and extending axially along part of the length thereof, the middle portion of said insert body defining an annular clearance between the ends of said body and the inner wall of said gun barrel, said ends of the insert body sealingly engaging said inner wall of the gun barrel; means for mounting an explosive charge in said barrel of an intensity less than that of a normal propulsive charge for ejecting shells from the barrel to produce gas at an elevated temperature, said clearance communicating with said charge whereby the hot charge gases pass through said clearance;

means for closing the breech end of said barrel on one axial side of said clearance; and

a rupturable plate closing said barrel on the opposite side of said clearance and sustaining a predetermined pressure in said clearance upon detonation of said charge but rupturing beyond said predetermined pressure.

2. The apparatus defined in claim 1 wherein said insert body is formed with the axial bore adapted to receive said charge, sealing rings at each end of said insert body engageable with the internal wall of said barrel to close said annular clearance at opposite axial ends thereof, radial bores between said sealing rings communicating between said axial bore and said clearance, said radial bore being disposed between said plate and said charge.

3. The apparatus defined in claim 1, further comprising an end cap fitting over a fore end of at least a part of said barrel and provided with a central bore, said plate being mounted in said bore; a threaded ring retaining said plate in said bore; a charge casing sealingly engageable with the rear end of said part of said gun barrel; and means securing said insert body between said end cap and said casing. 

1. An apparatus for testing guN barrels by simulating actual firing stresses without a projectile therein comprising: a gun barrel; an insert body mounted in the loading chamber of said gun barrel to reduce the volume of said loading chamber and extending axially along part of the length thereof, the middle portion of said insert body defining an annular clearance between the ends of said body and the inner wall of said gun barrel, said ends of the insert body sealingly engaging said inner wall of the gun barrel; means for mounting an explosive charge in said barrel of an intensity less than that of a normal propulsive charge for ejecting shells from the barrel to produce gas at an elevated temperature, said clearance communicating with said charge whereby the hot charge gases pass through said clearance; means for closing the breech end of said barrel on one axial side of said clearance; and a rupturable plate closing said barrel on the opposite side of said clearance and sustaining a predetermined pressure in said clearance upon detonation of said charge but rupturing beyond said predetermined pressure.
 2. The apparatus defined in claim 1 wherein said insert body is formed with the axial bore adapted to receive said charge, sealing rings at each end of said insert body engageable with the internal wall of said barrel to close said annular clearance at opposite axial ends thereof, radial bores between said sealing rings communicating between said axial bore and said clearance, said radial bore being disposed between said plate and said charge.
 3. The apparatus defined in claim 1, further comprising an end cap fitting over a fore end of at least a part of said barrel and provided with a central bore, said plate being mounted in said bore; a threaded ring retaining said plate in said bore; a charge casing sealingly engageable with the rear end of said part of said gun barrel; and means securing said insert body between said end cap and said casing. 